Jago, I suppose, is akin to Yago, Santiago, Diego, Jacobo, Jacob, Giacomo, etc. Therefore it means both "supplanter" and "holder of the heel" and it's pronounced "ya" (like when a Russian says "yes") and "go" (when someone orders another person to "move on" but withouth the final "w" sound seen in the onomatopeya of a barbie-girl who reacts to a cute action in tv and says "awwww" and makes a cute face herself)